A loudspeaker including a yoke, magnet 103 and a magnetic circuit integrated unitarily into a frame is disclosed in Japanese Patent Laid-Open Publication No. 4-362900.
FIG. 4 is a sectional view of a conventional loudspeaker. Cylindrical yoke 101 having a bottom is made of magnetic material, such as iron. Frame 102 made of resin is fixed at an outer periphery of yoke 101 by being inserted with pressure or molding. Magnet 103 is spaced from inner surface 101a of a side wall of yoke 101 by a predetermined interval and is bonded to the bottom of yoke 101. Plate 104 is bonded on an upper surface of magnet 103 and provides magnetic gap 104a between the plate and inner surface 101a of yoke 101. Diaphragm 105 is formed by molding a resin sheet. Voice coil 106 is positioned in magnetic gap 104a and has an end bonded on a lower surface of diaphragm 105.
Voice coil 106 is formed by winding a coil wire having a heat welding layer on its surface and coated for insulating and heating the wound wire. Coil terminals 106a, both end portions of voice coil 106, are led from between diaphragm 105 and yoke 101, and connected by soldering to respective ends of external terminals 107 integrated with frame 102.
In the structure mentioned above, a sound signal is supplied from an external sound source through external terminals 107 to voice coil 106, and the voice coil 106 and diaphragm 105 vibrate to generate a sound.
The conventional loudspeaker is to be thin and make a large output for use in a portable communication device, such as a portable telephone, and coil terminals 106a led from between diaphragm 105 and yoke 101 may contact diaphragm 105 or yoke 101 according to a vibration of the loudspeaker driven, thereby producing a noise. The conventional loudspeaker accordingly requires a certain interval between diaphragm 105 and yoke 101, thus being prevented from having a reduced size.